Adjustment drive

ABSTRACT

There is described an adjustment drive for a motor vehicle, in particular for a camshaft adjuster of an internal combustion engine, wherein the adjustment drive is constructed as a three-shaft transmission, having a transmission input shaft (NAR), an adjustment shaft (VW) which drives an eccentric tappet (EL, ZEL) which supports an externally toothed transmission element (GE), a gearwheel, and a transmission output shaft (GP) which is coupled to an internal gear (HR) which interacts with the externally toothed transmission element (GE) driven by the eccentric tappet (EL, ZEL) of the adjustment shaft (VW), the gearwheel, with a torque support between transmission input shaft and the externally toothed transmission element which has elastic coupling elements (FE).

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a U.S. National Stage of International Application No. PCT/EP2014/056198 filed Mar. 27, 2014, which claims the benefit and priority of German Application No. DE102013207253.8 filed Apr. 22, 2013 and German Application No. DE102613215816.5 filed Aug. 9, 2013. The entire disclosure of each of the above applications is incorporated herein by reference.

TECHNICAL FIELD

The invention relates to an adjustment drive for a motor vehicle, in particular for a camshaft adjuster of an internal combustion engine, constructed as a three-shaft transmission having a transmission input shaft, an adjustment shaft which drives an eccentric tappet supporting an externally toothed transmission element, a gearwheel, and a transmission output shaft which is coupled to an internal gear which interacts with the externally toothed transmission element driven by the eccentric tappet of the adjustment shaft.

BACKGROUND

Adjustment drives constructed as a three-shaft transmission serve, for example, to adjust the camshaft of an internal combustion engine. The camshaft driven at half speed by the crankshaft can be adjusted in terms of the phase position, the use of the inlet and outlet valves can be adapted to the power requirements of the mode of operation of the engine.

Adjustment drives constructed as eccentric transmissions are known. One input shaft is coupled via a chain drive to the crankshaft, the second input shaft, the adjustment shaft to an adjustment motor. This brings about the adjustment of the phase position of the output shaft—camshaft—with respect to the input shaft.

EP 1 039 101 A2 describes an adjustment drive which is embodied as a harmonic drive and is coupled to a disc motor.

An eccentric transmission which is embodied as a three-shaft transmission comprises a transmission input shaft, an externally toothed transmission element (externally toothed gearwheel) which is mounted rotatably on an eccentric pin of an eccentric shaft, the adjustment shaft, as well as an internal gear which corresponds to the transmission output and which is coupled to the output shaft, the camshaft. The number of teeth of the internal gear and that of the externally toothed transmission element is different and determines the transmission ratio.

The externally toothed transmission element of the adjustment shaft is in engagement with the internal gear and runs eccentrically. This gearwheel is mounted rotatably with respect to the eccentric shaft or an eccentric tappet coupled to the adjustment shaft. In order to bring about an adjustment, rotation of the internal gear, the output shaft with a rotating eccentric tappet, the gearwheel, the transmission element is supported in a rotationally conjoint manner. The torque support mounting which brings this about must not restrict the eccentric movement of the transmission element.

WO 2005059401 A1 discloses an eccentric gearwheel transmission with a flexible coupling element.

SUMMARY

The object of the present invention lies in proposing an adjustment drive in an embodiment which is improved in comparison with the known solutions.

This object is achieved by the combination of elements set forth in independent claim 1. Further developments will become apparent from the subordinate claims.

According to the invention, an adjustment drive for a motor vehicle, in particular for a camshaft adjuster of an internal combustion engine, is provided, wherein the adjustment drive is constructed as a three-shaft transmission, having a transmission input shaft, an adjustment shaft which drives an eccentric tappet which supports an externally toothed transmission element, a gearwheel, and a transmission output shaft which is coupled to an internal gear which interacts with the externally toothed transmission element driven by the eccentric tappet of the adjustment shaft, the gearwheel, with a torque support between transmission input shaft and the externally toothed transmission element which has elastic coupling elements.

In further developments, it is provided:

-   -   the torque support has a central middle part which sits         centrally and substantially tangentially running arms between         the middle part and the transmission input shaft or the middle         part and the externally toothed transmission element.     -   the arms have in each case a bending joint in the region of the         linkage at the middle part.     -   the central middle part is connected via in each case a pair of         arms to the transmission input shaft and the externally toothed         transmission element.     -   an arm between middle part and transmission input shaft or         middle part and externally toothed transmission element         comprises in each case two webs running parallel to one another.     -   the torque support comprises a plate, preferably of spring         steel, which has the elements which serve the purpose of elastic         coupling cut out.     -   wherein the adjustment drive is formed as a camshaft adjuster of         an internal combustion engine, wherein the transmission input         shaft is a camshaft drive wheel driven by the crankshaft of the         internal combustion engine, the adjustment shaft is driven by a         preferably electric drive and the internal gear is coupled to         the camshaft.

The adjustment drive according to the invention thus comprises a three-shaft transmission, having a transmission input shaft, an adjustment shaft which drives an eccentric tappet which supports an externally toothed transmission element, a gearwheel, and a transmission output shaft which is coupled to an internal gear which interacts with the externally toothed transmission element driven by the eccentric tappet of the adjustment shaft, the gearwheel, with a torque support between transmission input shaft and the externally toothed transmission element which has elastic coupling elements in the radial direction. The coupling elements act in the direction of rotation rigidly, stiffly, enable, as a result of the elasticity in the radial direction, the free movement of the gearwheel running on the eccentric tappet and its coupling to the transmission input shaft.

The torque transmission, torque support between the externally toothed transmission element and the camshaft drive wheel is produced by a special component (clutch element). The component has both elastic and very rigid regions so that it can transmit on one hand torque (as rotationally rigid as possible) between two axially offset shafts (externally toothed transmission element, running eccentrically and a centrally rotating wheel—the camshaft drive wheel), but does not influence the radial axial offset of these two parts. The radial offset between these parts is defined by the eccentricity value of the eccentric shaft (supports and drives the transmission element).

The guide element comprises according to one preferred embodiment of the invention at least two types, pairs of arms and a rigid middle part. The arms are ideally in each case parallel to one another. The arms are furthermore ideally arranged at a right angle to the further arms. All these arms contribute to the transmission of torque between the externally toothed transmission element (guided eccentrically above the eccentric tappet) and the camshaft drive wheel by virtue of the fact that they accommodate in each case tractive and compressive forces. The arms are ideally also at a maximum distance from one another so that the forces to be transmitted remain as low as possible with corresponding torque transmission. All these arms are embodied at their two ends in each case to be very thin and thus very pliable so that these pliable regions act as pivot bearings.

A pair of arms is connected to the camshaft drive wheel via pins and allows via their correspondingly elastic pivot bearings with very little force outlay a displacement of the rigid middle part in the perpendicular direction to these arms, wherein these arms can transmit torque from the camshaft drive wheel to the rigid middle part. A corresponding torque at this middle part is then passed on with the arms to the externally toothed transmission element.

The resiliently flexible pivot bearings of one pair of arms allow a displacement of the externally toothed transmission element in the perpendicular direction to the further pairs of arms with respect to the middle part with very little force outlay. This flexible guide element thus holds the externally toothed transmission element radially resiliently and does not guide it radially with respect to the camshaft drive wheel, rather transmits torque between these two parts.

DRAWINGS

The explanation of an exemplary embodiment of the invention is furthermore made on the basis of the drawings.

FIG. 1 is an exploded perspective view of an eccentric transmission, particularly adapted for use as an adjustment transmission for a cam adjuster of an internal combustion engine, constructed in accordance with an embodiment of the present invention;

FIG. 2 is an assembled side view of the adjustment transmission of the present invention shown in a nominal, unrotated starting position;

FIG. 3 is generally similar to FIG. 2 but illustrates an internal gear rotated about 10° with respect to a camshaft drive wheel of the adjustment transmission;

FIG. 4 is similar to FIG. 3 with the exception that a flexible guide element has been omitted for clarity purposes;

FIG. 5 is a sectional view of the adjustment transmission taken generally along line A-A of FIG. 3;

FIG. 6 is a sectional view of the adjustment transmission taken generally along line C-C of FIG. 5;

FIG. 7 is a side view of the flexible guide element;

FIG. 8 is a perspective view of the flexible guide element; and

FIG. 9 is an assembled perspective view of the adjustment transmission according to the invention.

DESCRIPTION

FIG. 1 shows, in a perspective representation, an eccentric transmission as an adjustment transmission for a camshaft adjuster. A base plate GP is coupled to the camshaft, not represented, connected directly thereto. An internal gear HR with an internal toothing is connected fixedly to base plate GP. This can be a single-piece formation—or two parts are pressed, welded.

Transmission element GE having an external toothing sits on an adjustment shaft VW shaped externally and eccentrically to its axis of rotation, which adjustment shaft VW is coupled to an electric adjustment drive, via an eccentric bearing EL with a bearing inner ring LI. O-rings OR (or spring elements) are assigned to bearing inner ring LI and push eccentric bearing EL in the direction of more eccentricity (play-free).

Bearing inner ring LI is fixed axially next to O-rings OR on adjustment shaft VW by means of retaining ring SRORLI. Adjustment shaft VW is mounted via a central eccentric bearing ZEL on a central pin ZZ of base plate GP.

Camshaft drive wheel NAR is mounted concentrically but rotatably with respect to base plate GP or internal gear HR. As FIG. 5 in particular shows, the camshaft drive wheel sits on internal gear HR, is rotatable with respect thereto and is fixed axially by means of retaining ring SNW.

A flexible guide element FE serves to transmit torque between externally toothed transmission element GE and camshaft drive wheel NAR—thus forms a coupling between the two elements, can thus also be referred to as a coupling element. This element FE does not bring about any guidance of externally toothed transmission element GE radially, i.e. in the directions transverse to the transmission axis—this moves in accordance with the driving eccentric tappet of adjustment shaft VW.

Flexible guide element FE is connected, coupled, by means of pins ST to camshaft drive wheel NAR. Pins ST sit in corresponding pin webs, receivers AST of camshaft drive wheel NAR. Transmission element GE mounted eccentrically on the axis of the transmission has on two opposing end side regions in each case an external toothing segment ASG in which the external toothing is increased in size across the width—and width corresponding to the engagement into the internal toothing of internal gear HR—of transmission element GE. These external toothing segments ASG serve to receive, articulate flexible guide element FE.

FIGS. 3 and 4 show, lying next to one another, the view of the adjustment transmission similar to in FIG. 2 —once with and once without flexible guide element FE. The representation in FIG. 3 corresponds to a position of internal gear HR rotated by approx. 10 degrees with respect to camshaft drive wheel NAR with respect to FIG. 2—the reference numbers are omitted. FIG. 2 shows the nominal position of the adjustment transmission—the unrotated starting position.

FIG. 5 shows section A-A according to FIG. 3. FIG. 6 shows section C-C according to FIG. 5.

FIG. 7 shows flexible guide element FE, the torque support in an enlarged representation—cf. also FIGS. 2 and 3. FIG. 8 represents flexible guide element FE in perspective. Flexible guide element, torque support FE is manufactured from spring steel and has four pliable arms A11, A12, A21, A22 which extend in the tangential direction, which at the respective free ends the linkage for camshaft drive wheel NAR and transmission element GE.

Arms A11, A12 serve to link guide element FE to transmission element GE—to this end the ends of arms A11, A12 have window-like receivers A-ASG which comprise outer toothing segments ASG, projecting in the axial direction, of transmission element GE and engage into the toothing of external toothing segments ASG.

Arms A21, A22 serve to link guide element FE to camshaft drive wheel NAR, to this end the ends of arms A21, A22 have in each case a pin plate STP at the free end, via which pin plate the linkage to camshaft drive wheel NAR, the assigned receivers, is realized by means of pins ST.

Arms A11, A12, A21, A22 are formed in each case as a pair of webs extending parallel to one another. The webs form in each case a bending element at the transition to the central part of guide element FE. The orientation, the profile of arms A11, A12, A21, A22 is such that tractive and compressive forces can be transmitted via arms A11, A12, A21, A22 as a result of the relative movement between transmission element GE and camshaft drive wheel NAR. In the center, the part of guide element FE has an opening through which the adjustment shaft engages—cf. FIG. 5. Arms A11, A12, A21, A22 the parallel webs of arms A11, A12, A21, A22 are embodied to be thinner at their transitions to the middle part of guide element FE or to the links—pin plate STP, receiver A-ASG, which results in a pliable articulation of arms A11, A12, A21, A22 with respect to the middle, central part of guide element FE. In accordance with the eccentric movements of transmission element GE with respect to camshaft drive wheel NAR, arms A11, A12, A21, A22 perform movements which oscillate with respect to the middle part —transmission elements GE are positionally fixed with respect to camshaft drive wheel NAR here.

FIG. 9 shows a perspective view of the adjustment transmission according to the invention with flexible guide element FE and its linkage to camshaft drive wheel NAR and transmission element GE.

LIST OF REFERENCE NUMBERS

-   GP Base plate -   HR Internal gear -   VW Adjustment shaft -   EL Eccentric bearing -   LI Bearing inner ring -   GE Transmission element -   OR O-ring -   SRORLI Retaining ring -   ZEL Central eccentric bearing -   ZZ Pin -   NAR Camshaft drive wheel -   SNW Retaining ring -   FE Flexible guide element -   ST Pin -   AST Receiver Pin -   ASG External toothing segment -   A11, A12 Arm -   A21, A22 Arm -   STP Pin plate 

1. An adjustment drive for a motor vehicle, in particular for a camshaft adjuster of an internal combustion engine, wherein the adjustment drive is constructed as a three-shaft transmission having a transmission input shaft, an adjustment shaft which drives an eccentric tappet which supports an externally toothed transmission element, a gearwheel, and a transmission output shaft which is coupled to an internal gear which interacts with the externally toothed transmission element driven by the eccentric tappet of the adjustment shaft, the gearwheel, having a torque support between the transmission input shaft and the externally toothed transmission element which has elastic coupling elements.
 2. The adjustment drive as claimed in claim 1, wherein the torque support has a central middle part and substantially tangentially running arms between the middle part and the transmission input shaft or between the middle part and the externally toothed transmission element.
 3. The adjustment drive as claimed in claim 2, wherein the arms have in each case a bending joint in the region of the linkage at the middle part.
 4. The adjustment drive as claimed in claim 2, wherein the central middle part is connected via in each case a pair of arms to the transmission input shaft and the externally toothed transmission element.
 5. The adjustment drive as claimed in claim 2, wherein the arms between the middle part and the transmission input shaft or between the middle part and the externally toothed transmission element comprises in each case two webs running parallel to one another.
 6. The adjustment drive as claimed in claim 1, wherein the torque support comprises a plate, preferably of spring steel which has the elements which serve the purpose of elastic coupling cut outs.
 7. The adjustment drive as claimed in claim 1, wherein the adjustment drive is formed as a camshaft adjuster of an internal combustion engine, wherein the transmission input shaft is a camshaft drive wheel driven by the crankshaft of the internal combustion engine, the adjustment shaft is driven by an electric drive, and the internal gear is coupled to the camshaft. 